Study On Anti-bending Structures Of Fast-growing Eucalyptus Bookcase Shelf

With the rapid development of the solid wood furniture industry,the consumption of natural forest timber has also increased rapidly.As the world’s second largest timber consumer country,China has also put a lot of restrictions on the use of natural forests.Therefore,people attach more and more importance to plantation forests.Plantation forests grow rapidly,but the materials are relatively poor,and the growth stress is large.Problems such as warping,shrinkage,and cracking are more likely to occur during drying and processing.Therefore,how to make fast-growing wood high-value-added materials has become one of the directions that needed to be explored and studied in the current academic field and practical production field.Taking fast-growing eucalyptus as example,the data was found that domestic literature is mostly elaborated from the perspective of micro-structure and other theoretical aspects,while foreign countries pay more attention to application practice,but lack normative research results.At the same time,we know the shelves of wooden bookcases are subject to heavy loads over a long period of time and are particularly prone to bending,that is,creep of the plates by early market research.Usually,there are two methods for relieving the shelves’bending,such as a thickening shelf and adding vertical plate under the shelf,but these two methods will have a certain impact on the overall aesthetic of the bookcase.Combining the comprehensive research on various aspects,it showed that the current study is relatively lacking from the structural view of the possibility of fast-growing eucalyptus as a furniture material,and there are few other solutions to the bookcase shelf bending problem.A survey of 27 bookcase shelves in home stores revealed that in order to save costs and time,manufacturers also use wood-based panels such as particleboard as shelf materials in many solid wood bookcases,while pure solid wood panes bookcases commonly adopt flat-panel puzzle,this simple structure form.Therefore,the innovation of this paper is to use the fast-growing eucalyptus as the main material for the shelf of the solid wood bookcase,and to try to strengthen the shelf by exploring the superior bending structure of the bookcase shelf so as to improve the exist problem in daily life.The problem is expected to be solved to better apply strengthened structures in our life and it also provides a practical idea for increasing the utilization rate of fast-growing materials in furniture.After meticulous surveying and statistical analysis of the survey bookcase,the size specifications that meet the needs of the market and suitable for the later test are determined.The five final test shelf structures are solid wood puzzle structure,frame panels,frame panels plus wood wear belt,flat puzzle plus metal wear belt and short puzzle plus metal wear belt.For each structure,9 parallel specimens were set,and five groups of specimens were subjected to short-term creep tests for about two hours on the condition of reasonable control of other variables that affected the creep of wood,and the corresponding bending creep data were obtained.After numerical calculation of the initial data,we get the corresponding results:(1)from the bending creep aspect,short puzzle plus metal wear belt>frame panels plus wood wear belt>solid wood puzzle structure>flat puzzle plus metal wear belt>frame panels;(2)bending creep of frame panels and flat puzzle plus metal wear belt are both less than 1mm,and their mean strains are less than 5%,which indicates that these two kinds of structure of the bending creep performance;(3)short puzzle plus metal wear belt’s ability of anti-bending is poor as compared to the other four kinds of structure,so this structure is not suitable to be used as bookcase shelf;(4)in terms of the strain range of the specimens of the same group,flat puzzle plus metal wear belt owns the most stable anti-strain ability,its strain range value is only 0.7%,while short puzzle plus metal wear belt is the most unstable,reaching 7.29%.This paper used Burgers creep model to do nonlinear fitting and analysis for relatively initial experimental data.During the fitting process,the results showed that the fitting correlation coefficient R~2 of five group structures were all higher than 0.975,which illustrated that the Burgers model which used to fit the situation of shelf structures’bending creep could get better fitting results and well describe the shelf structures’load behaviors.At the same time,we got the results of parameters A,B,C,D,which represents the three different stages of the creep.A represents the first stage of the instantaneous elastic deformation,the deformation and stress is mainly related to the size,difference between five groups of structural transient elastic deformation also indicates that in the force moment,the anti-bending capacity of the frame panels was the best,flat puzzle plus metal wear belt took second place,and short puzzle plus metal wear belt was the worst.B and C represent the second stages of the delayed elastic deformation,bending creep process of the shelf get into the slow growth stage,the rate of bending is almost constant.At this stage,the deformation and deformation rate of short puzzle plus metal wear belt were the largest,the performances of frame panels and flat puzzle plus metal wear belt were both good.D represents the third stage of plastic deformation.The fitting parameter showed that the plastic deformation of the other four groups is of little different except for short puzzle plus metal wear belt.It was further explained that short puzzle plus metal wear belt is not suitable for the application structure of bookshelf.In addition,this paper also calculated and analyzed the relaxation time and delay time of the five groups,which can be used for comparing different structures’anti-permanent deformation performance and deformation rate,the results showed that:(1)the resistance to permanent deformation:flat puzzle plus metal wear belt>frame panels>solid wood puzzle structure>frame panels plus wood wear belt>short puzzle plus metal wear belt;(2)the deformation rate:short puzzle plus metal wear belt>frame panels plus wood wear belt>solid wood puzzle structure>flat puzzle plus metal wear belt>frame panels.Therefore,from the current analysis results,in these five structures,frame panels and flat puzzle plus metal wear belt are preferentially recommended and chosen as bookcases’shelf.The former is better when considering the aesthetics;but the latter is better if the flatness of the plate surface and the convenience of the processing are considered in a deep step.